Diabetic retinopathy (DR) is the leading cause of blindness in adults 20 to 74 years of age. Detecting early stage retinopathy prior to the onset of clinical findings would greatly impact the management and treatment of DR. The goal of this proposal is to develop new tests that could serve as screening or diagnostic tools for early DR. We have identified several tests that show dysfunctional changes prior to the onset of clinically-significant vascular lesions induced by diabetes. These tests need to be further evaluated to establish 1) the relationship between theses functional changes in retinal neurons and late stage vascular lesions that cause vision loss; 2) the temporal progression of the retinal vascular and neuronal changes to determine predictability of the test for vision loss; 3) the sensitivity and specificity of the tests to posiively detect retinopathy while identifying normal retinas and 4) if identification of early stage DR provides an earlier window for intervention. The study design also provides a unique opportunity to determine the pathophysiological mechanisms underlying early stage DR. In this proposal, we will pursue the following aims: Aim 1: Identify non-invasive objective measures to diagnose preclinical DR. We will determine if the appearance of reactive oxygen species (ROS) occurs simultaneously with retinal and visual dysfunction in early stage DR and if this correlates with late stage pericyte dropout and acellular capillaries. Receiver operating characteristic (ROC) analysis will be used to determine detection threshold for each test. Aim 2: Elucidate the mechanisms underlying early stage DR by evaluation the timecourse of oxidative stress and neuronal and vascular dysfunction. To investigate the underlying mechanisms of early DR, we will use functional data and carefully chosen ex vivo markers to determine if early-stage vascular changes in DR induce hypoxia which leads to neuronal changes or if early-stage neuronal changes produce an inflammatory response which initiates vascular dysfunction. Aim 3. Determine if treating early stage diabetic retinopathy prevents the progression of DR. We will investigate three therapeutic approaches: a general anti-oxidant (AREDS anti-oxidant supplement), a dual acting anti-oxidant/anti-apoptotic agent (tauroursodeoxycholic acid (TUDCA)) and insulin. Each approach will be applied either at the onset of the earliest neuronal dysfunction as detected by our non-invasive detection tools or at clinical onset of retinopathy as indicated by pericyte dropout and fluorescein leakage. This aim will determine if early intervention prevents late stage vascular changes. This proposal will establish detection tools of early DR and determine the efficacy of early intervention to prevent disease progression. These studies use rodent models of both Type I and Type II diabetes to establish utility and potential mechanistic connections that are clinically inaccessible. We have crafted detection tools by combining clinically available devices (ERG, SLO, retinal photography) with novel stimuli, conditions, or contrast agents to facilitate rapid clinical translation. Detecting early sage retinopathy prior to the onset of clinical findings and vision loss would greatly improve the management and treatment of DR. The results of these studies will establish a set of objective measures for detection of early stage DR that will be tested in human subjects in future studies.